Gifted Issues Discussion homepage Forums Identification, Testing & Assessment WJ versus WIAT question(s)

DS8 was tested on the WJ-III, but just when I thought I had completed my own achievement test by learning all about it, DD6 was tested on the WIAT. Sigh. I would rest on my WJ laurels, if not for an upcoming school meeting that promises to be challenging and at which DD's achievement scores will be a key topic.

I would be grateful for any thoughts on how the two tests compare and any relative strengths and weaknesses they may have. Are they pitched to different learning styles or skills? What should I know about the WIAT before waving the scores around?

Another reason I am interested in any differences between the tests is that DD6 scored higher on the WISC (GAI 99.8) than DS8 (GAI 98), but their achievement scores seem closer, to my entirely untrained eye (total achievement DD 135, DS 130). I should add that DS was diagnosed with dysgraphia post testing and I do not know if, or to what extent, that may have impacted on his scores.

My kids haven't taken the WIAT, so I'm not familiar with past knowing that it's a set of achievement tests. Re dysgraphia - you will see the impact of dysgraphia in any subtests that require a written response (including possibly math subtests). My dysgraphic has a very distinct pattern on the WJ-III Achievement subtests - subtests requiring verbal responses had scores near to his GAI percentage, subtests requiring a handwritten response (but untimed) had scores that were significantly lower, and subtests requiring handwritten response *and* timed were another SD (or more) lower across the board.

You might try googling "WIAT subtest descriptions" to find info on the subtests.

Best wishes,

polarbear

General comment: all tests have confidence intervals (standard error of measurement). The difference between 135 and 130 is well within standard error for most tests. And that's for administrations of the same test. When you consider the differences between tests, the standard error would be even more generous. I wouldn't put any weight at all on the difference in total achievement. The difference between 98%ile and 99.8%ile borders on significance. It's possible there is a genuine difference, but also not. Were they tested at the same time, or some years apart? The second test administered might be expected to have slightly higher scores, due to the Flynn effect.

As to the WJ and WIAT themselves: I prefer the WIAT, based on the subtests it has, especially the reading comprehension, oral reading fluency, and written expression subtests. The WJ has the advantage of fluency measures for reading, writing, and mathematics (WIAT only has reading and mathematics), which can be important for a diagnosis of dysgraphia (due to the impact of fine motor speed). OTOH, the WJ has a much higher ceiling, as it was normed through the ninth decade of life. (Guessing it was a pretty small and skewed sample, though!) The WIAT is normed through post-secondary, but really only has material up through the 12th grade/first-year college. For a six-year-old, the ceiling should not be a significant factor (and if it is, I think you should have plenty of ammo for acceleration!), with the following exception. One issue that does come up with the WIAT with very high-functioning kids is that there may be underestimates of ability on certain subtests, because of the item sets, which are administered based on age/grade (although a savvy examiner might select a set based on an estimate of skill level). For example, if your six-year-old is finishing first grade, but functioning at a fourth grade level in reading, she will still be administered the first grade item set, which is designed to collect meaningful normative information on the majority of first-graders, including those functioning +/- 2SDs from the mean. Except that your 6 yo might be +3 SD, so she may bang her (figurative) head on the ceiling of the item set, resulting in a probable low estimate of her actual reading comprehension skills. If she has done so, the examiner can determine if that is the case by how closely she approached the max raw score on the subtest. The subtests with this kind of age/grade-determined item set are reading comprehension and oral reading fluency.

The WJ also has a number of additional subtests that can be useful for additional probing, such as spelling of sounds (spelling nonsense words, which exposes encoding weaknesses in individuals who have memorized spelling words without a strong grasp of the phonetic system). However, these subtests are rarely administered in standard batteries.

Thanks, both of you. Polarbear, I once charted DS's scores using your breakdown (found in another thread a while back) and it was eye-opening to see the impact of his dysgraphia laid bare.

Aeh, DS took the test at 6.5 years and DD took it at 6.25 years. Thank you for the explanation of the age/grade impact, it explains the reading tests. DD just finished kindergarten and had a perfect score on the early reading subtest, so she was given the reading comprehension subtest, as well (grade 4 result).

My daughter also had a perfect score on the WIAT reading comprehension and I've thought ever since that the WJ would be better if we ever did achievement testing again because of that ceiling issue. From what I'm reading here, though. It would be possible for the examiner to work around that. So would we just ask for a different level or extra leel to be used and just get a grade level equivalent as a standard score or percentile wouldn't be available for that score for younger ages?

apm, yes. It looks like CoastalMom's DD did have a reading comprehension item set administered out-of-level, as she was probably on the kindergarten norms, to begin with, and shouldn't have had rc. Although at age six, one could place her on the first grade norms, and derive grade-based standard scores.

CM, I asked about when your children had the WISC because that might account for some of the difference in GAI. Your children were compared to children who were age 6 in 2002 (when the norms were gathered), which is 10 years from your first DC, and 12 years from your second DC. The Flynn effect says that scores rise with distance from the norm group (about 3 pts every 10 years for the general public in the USA, but with some research suggesting a steeper rate for the gifted population). (Conversely, previously-identified gifted sometimes have a noticeable drop in measured IQ on switching to current norms (say, if you retested your DD in the next year, on the WISC-V).) A two year difference in distance from the norms is probably not responsible for a significant part of their GAI difference.